Brugada

Brugada syndrome is caused by sodium channelopathies that are more densely found in the right ventricle (producing findings in the rightward precordial leads). Patients with this disorder are predisposed to malignant ventricular arrhythmias, syncope, and sudden cardiac death. Although it is an inherited condition, patients commonly do not have a family history as there is a spontaneous mutation. Diagnosis relies on EKG and clinical findings. The EKG findings may be transient and brought out by fever, temperature abnormalities, electrolyte abnormalities, and multiple medications/drugs. The clinical criteria are VF/VT, inducible VT, family history of early sudden death, syncope, and nocturnal agonal respirations. 

There are now 2 main types of EKG findings (formerly 3 types). The first type is diagnostic of Brugada syndrome with a clinical entity. Type I is characterized by a coved ST elevation >2mm in multiple right precordial leads followed by a negative T wave. It has a coved appearance as it is difficult to clearly identify the J point between the R' and ST segments (slowly downslopes from the R' wave). 

Type 2 EKG findings are not diagnostic, but are suggestive of Brugada syndrome if the patient has the above clinical criteria. This used to be divided into 2 types, though it was combined as there is no clinical difference between the old type 2 and type 3 EKG findings. This consists of either >2mm saddleback ST elevation in multiple right precordial leads or either of the above morphology but the ST elevation is <2mm. The saddleback elevation is called such as the R' looks like elevation, followed by downsloping ST segment, followed by upsloping ST segment into the T wave. 

The QRS pattern in the right precordial leads is often described as a pseudo-RBBB pattern due to the beta angle. It is vital to be able to differentiate these findings from lead misplacement as type 2 is usually overcalled due to misplacement of leads V1 and V2. If they are placed too high on the chest, it can produce an incomplete RBBB pattern that somewhat mimics Brugada findings. Please see the discussion of lead misplacement for further information on that. However, another way to differentiate a true incomplete/complete RBBB and Brugada findings is the beta angle. The beta angle is the angle between the ascending limb of the R' and the downslope of the ST segment. The beta angle needs to be at least 35* to have a type 2 pattern. A true incomplete RBBB or a fake IRBBB due to lead misplacement will have a very narrow beta angle.

Some medical conditions can mimic a Brugada phenocopy (Brugada pattern) that is usually type 1. Hyperkalemia is probably the most common of these, though hyponatremia/sodium channel blocker toxicity and hyperthermia (as well as numerous others) may produce somewhat similar findings. This is a large reason for the need for clinical correlation for diagnosis. Sometimes, the anterior ST elevation is thought to be from an OMI; the clinical picture will likely point away from an OMI. Additionally, patients with OMI rarely have evidence of RV conduction delay (ie the R').  Furthermore, the ST changes with Brugada syndrome will always have an abnormal QRS as well (repolarization abnormality with the depolarization abnormality). 

Examples:

Further Reading:

https://litfl.com/brugada-syndrome-ecg-library/

http://hqmeded-ecg.blogspot.com/search/label/Brugada%20pattern

http://hqmeded-ecg.blogspot.com/search/label/brugada

https://www.onlinejacc.org/content/72/9/1046?_ga=2.247224589.869150275.1567990447-155531933.1567990447